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diff --git a/doc/misc/layers.txt b/doc/misc/layers.txt deleted file mode 100644 index a02e481..0000000 --- a/doc/misc/layers.txt +++ /dev/null @@ -1,222 +0,0 @@ -pdp 0.13 design layers + components ------------------------------------ - -from version 0.13 onwards, pdp is no longer just a pd plugin but a -standalone unix library (libpdp). this documents is an attempt to -describe the design layers. - -A. PD INTERFACE ---------------- - -on the top level, libpdp is interfaced to pd using a glue layer which -consists of - -1. pdp/dpd protocols for pd -2. process queue -3. base classes for pdp/dpd -4. some small utility pd objects -5. pd specific interfaces to part of pdp core -6. pdp_console -7. pd object interface to packet forth (pdp object) - - -1. is the same as previous versions to ensure backwards compatibility in -pd with previous pdp modules and extensions that are written as pd -externs or external libs. this includes parts of pdp that are not yet -migrated to libpdp (some of them are very pd specific and will not be -moved to libpdp), and pidip. if you intend to write new modules, it is -encouraged to use the new forth based api, so your code can be part of -libpdp to use it in other image processing applications. - -2. is considered a pd part. it implements multithreading of pdp inside -pd. multithreading is considered a host interface part, since it usually -requires special code. - -3. the base classes (pd objects) for pdp image processing remain part of -the pd<->pdp layer. the reason is the same as 1. a lot of the original -pd style pdp is written as subclasses of the pdp_base, pdp_image_base, -dpd_base and pdp_3dp_base classes. if you need to write pd specific -code, it is still encouraged to use these apis, since they eliminate a -lot of red tape involving the pdp protocol. a disadvantage is that this -api is badly documented, and the basic api (1.) is a lot simpler to -learn and documented. 3dp is supposed to merge to the new forth api, -along with the image/video processing code. - -4. is small enough to be ignored here - -5. includes interfaces to thread system and type conversion system + -some pd specific stuff using 1. or 3. - -6. the console interface to the pdp core, basicly a console for a -forth like language called packet forth which is pdp's main scripting -language. it's inteded for develloping and testing pdp but it can be -used to write controllers for pd/pdp/... too. this is based on 1. - -7. is the main link between the new libpdp and pd. it is used to -instantiate pdp processors in pd which are written in the packet forth. -i.e. to create a mixer, you instantiate a [pdp mix] object, which would -be the same as the previous [pdp_mix] object. each [pdp] object creates -a forth environment, which is initialized by calling a forth init -method. [pdp mix] would call the forth word init_mix to create the local -environment for the mix object. wrappers will be included for backward -compatibility when the image processing code is moved to libpdp. - - -B. PDP SYSTEM CODE ------------------- - -1. basic building blocks: symbol, list, memory manager -2. packet implementation (packet class and reuse queue) -3. packet type conversion system -4. os interface (X11, net, png, ...) -5. packet forth -6. additional libraries - - -1. pdp makes intensive use of symbols and lists (trees, stacks, queues). -pdp's namespace is built on the symbol implementation. a lot of other -code uses the list - -2. the pdp packet model is very simple. basicly nothing more than -constructors (new, copy, clone), destructors (mark_unused (for reuse -later), delete). there is no real object model for processors. this is a -conscious decision. processor objects are implemented as packet forth -processes with object state stored in process data space. this is enough -to interface the functionality present in packet forth code to any -arbitrary object oriented language or system. - -3. each packet type can register conversion methods to other types. the -type conversion system does the casting. this is not completely finished -yet (no automatic multistage casting yet) but most of it is in place and -usable. no types without casts. - -4. os specific modules for input/output. not much fun here.. - -5. All of pdp is glued together with a scripting language called packet -forth. This is a "high level" forth dialect that can operate on floats, -ints, symbols, lists, trees and packets. It is a "fool proof" forth, -which is polymorphic and relatively robust to user errors (read: it -should not crash or cause memory leaks when experimenting). It is -intended to serve as a packet level glue language, so it is not very -efficient for scalar code. This is usually not a problem, since packet -operations (esp. image processing) are much more expensive than a this -thin layer of glue connecting them. - -All packet operations can be accessed in the forth. If you've ever -worked with HP's RPN calculators, you can use packet forth. The basic -idea is to write objects in packet forth that can be used in pd or in -other image processing applications. For more information on packet -forth, see the code (pdp_forth.h, pdp_forth.c and words.def) - -6. opengl lib, based on dpd (3.) which will be moved to packet forth -words and the cellular automata lib, which will be moved to -vector/slice forth later. - - -C. LOW LEVEL CODE ------------------ - -All the packet processing code is (will be) exported as packet forth -words. This section is about how the code exported by those words is -structured. - -C.1 IMAGE PROESSING: VECTOR FORTH - -Eventually, image operations need to be implemented, and in order -to do this efficiently, both codewize (good modularity) as execution speed -wize, i've opted for another forth. DSP and forth seem to mix well, once -you get the risc pipeline issues out of the way. And, as a less rational -explanation, forth has this magic kind of feel, something like art.. -well, whatever :) - -As opposed to the packet forth, this is a "real" lowlevel forth -optimized for performance. Its reason of being is the solution of 3 -problems: image processing code factoring, quasi optimal processor -pipeline & instruction usage, and locality of reference for maximum -cache performance. Expect crashes when you start experimenting with -this. It's really nothing more than a fancy macro assembler. It has no -safety belts. Chuck Moore doctrine.. - -The distinction between the two forths is at first sight not a good -example of minimizing glue layers. I.e. both systems (packet script -forth and low level slice forth) are forths in essence, requiring -(partial) design duplication. Both implementations are however -significantly different which justified this design duplication. - -Apart from the implementation differences, the purpose of both languages -is not the same. This requires the designs of both languages to be -different in some respect. So, with the rule of "do everything right -once" in mind, this small remark tries to justify the fact that forth != -forth. - -The only place where apparent design correspondence (the language model) -is actually used is in the interface between the packet forth and the -slice forth. - -The base forth is an ordinary minimal 32bit (or machine word -lenght) subroutine threaded forth, with a native code kernel for -i386/mmx, a portable c code kernel and room for more native code kernels -(i.e i386/sse/sse2/3dnow, altivec, dsp, ...) Besides support for native -machine words bit ints and pointers, no floats, since they clash with -mmx, are not needed for the fixed point image type, and can be -implemented using other vector instructions when needed), support for -slices and a separate "vector stack". - -Vectors are the native machine vectors, i.e. 64bit for mmx/3dnow, -128bit for sse/sse2, or anything else. The architecture is supposed to -be open. (I've been thinking to add a block forth, operating on 256bit -blocks to eliminate pipeline issues). Blocks are just blocks of vectors -which are used as a basic loop unrolling data size grain for solving -pipeline operations in slice processing words. - -Slices are just arrays of blocks. In the mmx forth kernel, they can -represent 4 scanlines or a 4 colour component scanline, depending on how -they are fed from packet data. Slices can be anything, but right now, -they're just scanlines. The forth kernel has a very simple and efficient -(branchless) reference count based memory allocator for slices. This -slice allocator is also stack based which ensures locality of reference: -a new allocated slice is the last deallocated slice. - -The reason for this obsession with slices is that a lot of video -effects can be chained on the slice level (scanline or bunch of -scanlines), which improves speed through more locality of reference. In -concreto intermediates are not flushed to slower memory. The same -principles can be used to do audio dsp, but that's for later. - -The mmx forth kernel is further factored down following another -virtual machine paradigm. After doing some profiling, i came to the -conclusion that the only, single paradigm way of writing efficient -vector code on today's machines is multiple accumulators to avoid -pipeline stalls. The nice thing about image processing is that it -parallellizes easily. Hence the slice/block thing. This leads to the -1-operand virtual machine concept for the mmx slice operations. The -basic data size is one 4x4 pixel block (16bit pixels), which is -implemented as asm macros in mmx-sliceops-macro.s and used in -mmx-sliceops-code.s to build slice operations. The slice operations are -built out of macro instructions for this 256bit or 512bit, 2 or 1 -register virtual machine which has practically no pipeline delays -between its instructions. - -Since the base of sliceforth is just another forth, it could be that -(part of) 3dp will be implemented in this lowlevel forth too, if -performance dictates it. It's probably simpler to do it in the lowlevel -forth than the packet forth anyway, in the form of cwords. - -C.2: MATRIX PROCESSING: LIBGSL - -All matrix processing packet forth words are (will be) basicly wrappers -around gsl library calls. Very straightforward. - -C.3: OPENGL STUFF - -The same goes for opengl. The difference here is that it uses the dpd -protocol in pdp, which is more like the Gem way of doing things. The -reason for this is that, although i've tried hard to avoid it, opengl -seems to dictate a drawing context based, instead of an object based way -of working. So processing is context (accumulator) based. Packet forth -will probably get some object oriented, or context oriented feel when -this is implemented. - - - - |